RT‐qPCR for the diagnosis of dermatophilosis in horses

Abstract

Results of this study show that RT-qPCR may be a more sensitive and easier method than cytological evaluation for the diagnosis of dermatophilosis in horses.

The prevalence of Dermatophilus congolensis in horses with pastern dermatitis using PCR to diagnose infection in a population of horses in southern USA

“…RT-qPCR for the diagnosis of D. congolensis was then performed as previously reported and validated. 5 Briefly, reactions consisted of 0.2 lM each of primers DCMP-FWD and DCMP-REV and FAM labelled probe, 19 ROX dye and 2 lL DNA in 29 master mix (TaqMan Universal PCR Master Mix, no AmpErase UNG taq polymerase, Thermo Fisher Scientific; Waltham, MA, USA) in a total volume of 20 lL. Samples were denatured at 95 degrees for 20 s followed by extension at 60 degrees for 20 s for 40 cycles (StepOne real-time PCR instrument, Thermo Fisher Scientific).…”

“…4 Multiple PCR assays have recently been validated for the detection of D. congolensis. 5,8,9 A study which utilized quantitative real time PCR (RT-qPCR) confirmed the increased sensitivity of this method compared to traditional cytological methods, where nine of 14 horses with suspect dermatophilosis were found to be cytologically positive for D. congolensis, whereas 11 of these horses were PCR positive. 5 This study demonstrated 100% sensitivity and 92% specificity for the diagnosis of D. congolensis with RT-qPCR when compared to cytological methods.…”

“…The organism is a known pathogen and is not found on the healthy skin of horses. 5 Dermatophilus congolensis has branching hyphae that form a railroad track appearance on cytological examination. [1][2][3][4][5] Despite this distinctive appearance and the organism's common occurrence in horses, it is often difficult to identify cytologically in chronic lesions.…”

“…5 Dermatophilus congolensis has branching hyphae that form a railroad track appearance on cytological examination. [1][2][3][4][5] Despite this distinctive appearance and the organism's common occurrence in horses, it is often difficult to identify cytologically in chronic lesions. 1,5,6 As many horse owners and handlers often attempt to treat pastern dermatitis empirically, these lesions are frequently chronic by the time a veterinary practitioner assesses them.…”

“…Aerobic bacterial culture is equally challenging due to frequent contamination and overgrowth by other bacteria. 1,5,6 A study investigated the association of D. congolensis with pastern dermatitis using cytological evaluation and culture. 4 The organism was only identified in two of 12 horses cytologically, only one of which was culture positive for the organism.…”